Method of forming titanium silicide coatings



- peratures.

United States Patent 0 3,047,419 METHOD OF FORMING TITANIUM SILICIDE COATINGS Leonard F. Yntema and StanleyyKluz, Waukegan, IlL,

assignors to Fansteel Metallurgical Corporation, a corporation of New York v No Drawing. Filed Feb. 26, 1954, Ser. No. 412,960

4 Claims. (Cl. 117-46) This invention relates to coating of massive titanium metal bodies, titanium alloy metal bodies which have a substantial titanium content, and other metal bodies which have been clad with titanium or titanium alloy, metal as a surfacing material for enhanced properties available from such titanium metal bodies and its alloys, the coating of the titanium body consisting essentially of titanium silicides which impart to the titaniumbase metal resistance to gaseous attack in high'temperatureruses thereof, particularly resistance to oxidation in air at high tem The invention more particularly relates to such titanium metal. and titanium metal alloy products having askin coating containing as the predominant component an alloy or intermetallic composition containing about 7 26% silicon and the balance titanium, namely Ti Si and to methods of forming these coated titanium metal and titanium metal alloy products.

The silicide coated titanium and titanium alloys containing a substantial quantity of titanium, at least about 5% titanium, have highly desirable properties in use at elevated temperatures. The desirable high temperature uses for silicide coated titanium metal and alloys thereof are as heatingelements, nozzles for rockets, artillery pieces, burners, blades and buckets for turbines, and other uses wherein the metal is exposed at high tempera tures to destructive gases, particularly oxygen in air, and wherein the inherent strength and light weight of the metal are desirably retained. In these several high temperature uses without the silicide coating of the present invention, it is usually necessary to exclude oxygen or other corrosive gases, and his common for this purpose to supply a continuous flow of inert gas to the heated metal parts to avoid oxidation or other gaseous attack at the raised temperatures.

According to the present invention, the titanium or titanium alloy base has formed thereon an integral skin coating of silicon and titanium as an alloy or intermetallic composition, to impart optimum protection to the titanium base for use at raised temperatures, especially use in air at temperaturesexceeding about 800 C., for long periods of time.

The alloy or intermetallic composition comprising the skin coating upon the titanium or alloy thereof consists essentially of a titanium silicide or a mixture of such silicides comprising the compound Ti Si which is a preferred component because it will resist fusion at temperatures up to about 2120 C., or a mixtures of Ti Si and TiSi- The titanium silicide compound TiSi has great utility when present in the skin coating upon the metal base because it will not melt at temperatures below about 1540 C. and because it enhances the resistance in air at high temperatures of the skin coating on the titanium base.

In general, in accordance with the present invention, the skin coating upon the titanium metal base is varied in proportions of silicon and titanium to produce titanium silicides in the skin coating variable in titanium-silicon ratios to encompass the compounds TiSi and Ti Si but preferably are adjusted to predominate in the higher melting'Ti Si Thus, the skin coating will generally vary in silicon content from about 20% to 65% by weight, preferably 26% to 54% by Weight, of the Skin Coating,

3,047,4 Patented July 31, 19

the balance being essentially titanium available from titanium base into which the silicon is sintered or a able from the alloys of the titanium with other me when the alloy is used, but the titanium content of skin coating may be supplied at least in part extranel ly with the silicon. Thus, the ratio of silicon to titan in the skin coating will generally range from abot parts of silicon to 1 part of titanium down to 3 part. silicon to 5 parts of titanium by weight of the skin to j duce a mixture variable between compositions of t] formulae, preferably containing, as stated, Ti Si as predominant component of the composition.

Although the optimum protection of the titanium 1 metal in air at temperatures above about 1500 C obtained with coatings or skins having a molecular r of about 3 parts of silicon to 5 parts of titanium, responding to a silicon content of about 26%, coat greater or less than that composition, such as com; tions in the range of 20% to 65% silicon, the bale being titanium, also afiord protection for the titan core or base at these high temperatures, and at lc temperatures may be more effective. For example, '1 is more effective in resisting oxidation in air at temp tures below about 1500 C. than is Ti Si Where it is indicated that the exterior skin comp! about 26% silicon and the balance titanium, this not mean that the exterior layer consists entirely of intermetallic compound of silicon and titanium ha the approximate percentage named, namely Ti Si that the exterior layer consists largely of that pure termetallic compound and may have associated wit more or less of the intermetallic compound of sil and titanium corresponding to 54% silicon and the ance titanium (TiSi preferably more, and/or sil in amount somewhat less than or in excess of that quired to form the preferred compound Ti Si and v in the range stated of about 20% to 65% silicon, balance being titanium.

These coatings or skins on the titanium or the titar alloy base furnish an exceedingly high resistance to 0) tion as well as destruction by other gases at elevated peratures. For example, it has been found that a co sample'of titanium according to this invention can r r oxidation fora period exceeding 2,000 hours when he in air at 800 0., whereas, in contrast, uncoated titar metal heated in air under similar conditions will usl be destroyed by oxidation in a period of less than hours.

These skin coatings, while they may be former. sintering of mixtures of titanium and silicon powder the surface of the base titanium metal or alloy the] or by sintering to such surface of preformed titanium cide powders, are generally formed by sintering or c heat application of elemental silicon alone to the sur of the base titanium metal or alloy thereof.

The thickness of such coating is most convenie measured herein as a thickness increase of the co metallic titanium body or alloy thereof, and accordi does not truly indicate the actual thickness of the c ing since the silicon, by sintering, has substantially p trated the surface comprising the original dimensi measurement of the uncoated base. In general, the coating of titanium silicide measured as a thicknes: crease should be at least A: mil in thickness and ma as thick as 15 mils, but such thicker coatings, while t ing progressively by increased thickness to give enha1 resistance of the base to oxidation in air, will oftel sult in reduced physical characteristics, such as flexi'l and other strength characteristics of the original titan and the coatings per .se may have increased tendenc crack or peel off. Accordingly, it is generally prefe to apply coatings up to about 10 mils in thickness,

here are several methods which may be used for ap- 1g the coating. Thus, the coating may be applied by :sing the heated metal titanium base or alloy thereof reducing atmosphere having therein vapors of reble compounds of silicon, such as a silicon halide, in iucing gas, such as hydrogen. If desired, such vapors also include vapors of titanium compounds for even rsition simultaneously of both titanium and silicon, re'by the skin coating is more readily controlled to therein the compound Ti Si nother procedure usefully followed for applying a do coating is with a flame spray, using a typical der gun applying elemental silicon powder as a spray heat either in a vacuum or inert gas as a carrier :for. ill another method is by cementation, which consists rally in embedding the titanium base metal in a fineawdered bed or bath of silicon powder, or a mixture ilicon and titanium powders, or a powdered pre- :red titanium silicide, the powder bath with the tilm work piece embedded therein being heated for ral hours, ranging from about 3 to 30- hours, to a ring temperature, usually about 900 to 1400 C. .lytic activators for the adhesion of the coating upon netal base, such as halogen, chlorine, bromine or ioor an alkali metal salt thereof, are desirably includn the powder in quantity of from a trace up to it 5%. Alternatively, an activating gas, such as chlomay be continuously passed in minute quantity ugh the powdered bed to activate the same during :ntation. nd still another method, preferred because of its most y applicability, is the application of the skin by paintpowders of silicon, or both silicon and titanium as rental mixtures of their powders, or powders of prered titanium silicides suspended as a slurry in a soluof a solvent containing a temporary and heat deposable binder therefor, first to adhere the powders surface film coating in proper proportion to the tilm or titanium alloy work piece, and then to decomthe binder substance and sinter the powder to the ium base metal as an integral skin layer thereon.

all of these methods a sutficiently thick coating may pplied as a single coating application, but it is pre- :d, particularly in the painting procedure, to apply a thin coating and then repeat the procedure to apadditional coatings thereon until the desired coating Lness has been obtained.

1e several coating procedures outlined above are variin utility by the degree of resistance to oxidation able, the even thickness of the coating obtainable, tendency of the coating to crack or peel off by the cular procedure used, and finally by the ready facility which the coating may be applied. From such conations, the paint method is preferred not only bea the apparatus and manipulation to obtain the coat- 5 simpler, but more even and reproducibly thick coatof constant physical and chemical characteristics are a readily available. Where a rough and uneven coats not objectionable, it is possible to apply a coating [icon in somewhat indefinite proportions by a hot dip edure wherein the metallic titanium or titanium alloy is merely dipped in a molten bath of elemental sili- C-130B is an alloy of Ti 92%, Mn 4% and Al 4%. l-150-A is an alloy of Ti 96%, Cr 2.7% and Fe 1.3%.

.4 here of the strips were removed and the strips were then blasted with grit for purposes of cleaning and slight roughening for best adhesion of the coating. The strips were then finally cleaned in a mixture of nitric and bydrofluoric acids.

PAINTING AND SINTERING METHOD This method consists of painting a suspension of coat-.

ing substance such as powder suspended as a slurry in a solvent containing an organic binder substance capable of decomposition by heat. The painting may be done with a paint spray gun or by hand brushing. The painted specimens are allowed to dry and are then sintered. The coating in each case is repeated until a. desired thickness of coating is obtained, such as a skin upon the titanium exceeding 0.5 mil in thickness, preferably about 1 to 3 mils.

The coating may exceed 10 mils in thickness, if desired, but such thicker coatings are not necessary and may even prove objectionable. While such coating may be applied by first coating anddrying in a series of treatments and finally sintering, it is preferable to sinter with each coat-- ing before the next coating is applied. There is some variation in the life of the coating with respect to oxidation resistance in air at high temperatures depending upon the method of sintering, the fineness of the metal powders being applied as a slurry in the wet coating to the titanium base, and the characters of the binder resin and carried liquid. Obviously, it is desirable that the coating be uniformly applied over the titanium to obtain a uniformly thick sintered coating.

(A) The Paint Resin The resin of this paint is selected to be a thermoplastic resin because of its superior property to be volatilized and/or decomposed at high temperatures upon sintering to leave no substantial carbonaceous residue, and for imparting fluidity and even thickness to this paint. Any typical thermoplastic paint resin which leaves no substantial carbonaceous residue when heated to temperatures exceeding its decomposition temperature, such as above about 1300 C., may be used herein. Such resin will be understood to be atypical temporary bonding resin to firmly adhere the powdered elements silicon or silicon and titanium to the titanium base and maintain the adhe sion until the resin is completely volatilized and/or decomposed. Alkyd resins are superior in this respect since they give good adhesion, good flow, hold the coating while heating, and leave no carbonaceous residue. Thermosetting resins, such as Bakelite, which leave a substantial deposit of carbon, are unsuitable. Typically useful resins are alkyd resins formed by reaction of polybasic organic acids such as phthalic acid, succinic acid, adipic acid, etc., with polyhydroxy aliphatic alcohols such as glycerin, ethylene glycol, etc., of which the reaction product of phthalic anhydride with glycerin, i.e. Glyptal resin, is preferred. The resin is applied in proportions of from 5% to 15%, usually about 10% by weight of the liquid carrier, and the quantity of resin related to powdered elements may range from about 1.5 to 3.5:1, usually about 2 to 3:1.

(B) The Solvent Desirable solvents, particularly for alkyd resins, are ketones. We may use any volatile ketone such as acetone, methyl ethyl ketone, diethyl ketone, diacetone alcohol, and preferably for a Glyptal resin, a mixture of diacetone alcohol and acetone in a ratio of about 7:3 parts by volume, respectively, may be used.

(C) Silicon or Silicon and Titanium or Titanium Silicide Powders The silicon is preferably fine commercial elemental silicon, about 97% pure, used in the form of a very finely powdered dust which will pass readily through a 325 mesh oreven finer screen. A desirable form of silicon is obtained by further classifying 325 mesh silicon by stirring a slurry thereof in water and pipetting off successive portions near the upper liquid surface to obtain an extremely fine elutriated silicon in this manner.

It is sometimes desirable to admix with the silicon, titanium or titanium hydride in proportions to approximate Ti Si or other proportions within the range given above for the desired silicon content, such as from 20% to 65% by weight silicon, the balance titanium. The powdered titanium metal per so when used with the silicon to coat the base also is substantially pure titanium metal, finely comminuted to a dust of about 325 mesh or less, the titanium and silicon powders being preferably uniformly sized and homogeneously admixed prior to suspending in the liquid paint carrier as a slurry, but they may be slurried into the liquid paint carrier in sequence, if desired. A]- ternatively, the titanium or a titanium hydride may be admixed with the silicon in proportions to form Ti Si or other titanium silicide such as in the proportion range given above, and the dry powders homogeneously admixed are presintered in a vacuum furnace having an inert atmosphere, such as helium or hydrogen, at a temperature of 1300 to 1800 C., preferably about 1500" C., to preform the titanium silicide. The presintered composition is then broken to fine fragments and milled to a powder of about 325 mesh or less, and this presintered powder is then suspended in a liquid paint carrier, as described for other powders, for furthering sintering upon the titanium metal base.

(D) Paint Coating The resin is first dissolved in a high boiling solvent as above identified, preferably Glyptal resin in a solvent comprising 7:3 volumetric mixture of diacetone alcohol and acetone respectively. The powder or powder mixture in the desired ratio is then stirred into the resin solution, for most purposes about 4 parts by weight of powder to 1 part by weight of resin, sufficient solvent being added to form a slurry that is readily applied by'hand brushing as a smooth flowing slurry. For spraying in a spray gun, the slurry may be somewhat thinner, namely, contain more solvent. The wet coated titanium metal, whether coated by hand brushing or spraying, is then placed in an air drying oven and dried at moderate temperatures, such as about 100 C. or less, to evaporate the solvent and produce a substantially dry adherent coating of powder temporarily bonded to the titanium base by the substantially dry alkyd resin.

(E) Sintering For sintering, the sample is placed in a furnace which may be either of two types:

(a) Helium furnace-This furnace consists of an Inconel tube, heated in a Nichrome-wound furnace. The work is placed in the Inconel tube through which helium is passed. The helium is purified by passage through magnesium perchlorate and then through tantalum gauze heated to 1000 C.

(b) Vacuum furnace.The vacuum furnace is of the induction type, consisting of a susceptor enclosed in a quartz tube. Power is supplied by an Ajax converter. An

'oil diffusion pump, backed by a mechanical pump, is used to evacuate the system.

In sintering the samples dried in the air drying oven after coating, the painted specimens are placed in grooves of a carrier block, such as an Alundum block or other inert carrier, and sintered either in the helium furnace or in the vacuum furnace maintained at a high vacuum, such as about microns or less, preferably the latter. The coated samples are desirably first preheated to an intermediate temperature, such as 300 to 400 C., for a short period of time, say 2 to 30 minutes, sufficient to volatilize and destroy the alkyd resin binder, but substantially the same effect is obtained if the green samples are merely brought up to sintering temperature slowly. According to the sintering procedure, the sample is placed in the carrier within the tube of the furnace and slowly heated over a 6 period of /2 to 2 hours, usually about an hour, to the sintering in a temperature ranging from about 1 up to about 1,400 0., preferably 1,200 to 1,400 C EXAMPLE 1 Titanium alloy (RC--B) in the form of 0 thick sheets was cut into strips 6" long by /2" wid sharp edges broken off and smoothed, and grit bl and cleaned by dipping in nitric and hydrofluoric The dried samples were then painted with a slurry parts of fine elu-triated silicon powder having an av mesh size of less than 325 (average particle size abor microns) mixed with a solvent comprising 7 parts acetone alcohol to 3 parts of acetone by weight, in l was dissolved 1 part of Glyptal resin by weight ratiot silicon powder, the quantity of solvent being such give a smooth flowing paint. The samples were painted and dried in an air oven for one hour. There the samples were placed in a helium furnace and h at 350 C. for 15 to 30 minutes to volatilize and de pose the Glyptal resin binder. The coated samples then placed in a furnace and sintered at temperatur from 1,000 to 1,400 C., generally about 1,300 C about an hour. By repeating the procedure, coatings produced having thicknesses ranging from 1 to 10 mil. the summary table below, tests of coatings obtain: this method are listed comparatively with tests upo coated product formed in other examples.

VAPOR PHASE DEPOSITION According to this method, the heated titanium metal has passed thereover vapors of a silicon halide, as silicon tetrachloride carried in a reducing gas Sut hydrogen, to reduce the silicon compound upon the metal, forming therewith an integral skin coating oi nium silicide. For vapor phase deposition, the ap tus may consist of a Vycor tube wrapped in coppe1 with heating supplied by an induction coil activated high frequency Ecco converter. The procedure is to purified hydrogen gas carrying therein controlled 1 tities of silicon tetrachloride or other volatile redi silicon compound. The hydrogen carrier gas is pu first by contacting it with a hot copper gauze maint at about 550 C., and then passing it through a m; sium perchlorate column. The purified hydrogen 1 then passed, as by bubbling, through a volatile, liqui ducible silicon compound, such as silicon tetrachlorii a rate to carry therewith a controlled quantity of s. tetrachloride vapor, and the mixed gas and vapor then passed through the Vycor tube in which the st of titanium to be coated is mounted. The titanium b to be coated are prepared in the same manner as desc in Example 1 and supported within the Vycor tu grooves of an Alundum block, a preferred type of su although similar supports of molydenum, silicon car or Ti Si may be used. The titanium body within the is heated by induction heat to a temperature withi range of about 875 to 1400 C. for short periods of a 5 to 15 minutes. The evenness of the coating is desi maintained by reversing the sample occasionally to t over with respect to its support and present an op end with respect to the flow of gases thereover. B1 method, coatings from about 0.5 to 3 mils in thic may be obtained. As in the painting method desc above, both silicon and titanium may be simultane deposited from their volatile halides, for example a ture of silicon tetrachloride and titanium tetrachli with simultaneous reduction and formation of a sk titanium silicides in the desired ratio.

EXAMPLE 2 The titanium samples according to Example 1 are ported within the Vycor tube, heated in the pref range at about 1000" to 1350" C. for two 5 minute ods; the first period being interrupted to reverse the ple in the tube and the second period thereafter ap Jgen is first purified by passing it through hot copper maintained at 550 C. and then through dry mag 11 perchlorate. It is then passed through liquid silietrachloride maintained at a temperature of about at a rate of about 800 cc. of hydrogen gas per minnd the vapor suspension then passed over the heated e in the tube, the heating being terminated after each i and the sample cooled in hydrogen gas alone. A 1g of good appearance of about 1 mil thickness is ted. Greater or lesser quantities of silicon tetra- .de may be supplied as a vapor in the hydrogen by 1g the temperature of the liquid silicon tetrachloride, igher the temperature the more vapors thereof being hydrogen. In a similar manner, both silicon tetraide and titanium tetrachloride vapors may be carn hydrogen gas, preferably by forming independent [T68 of the volatilized halides in hydrogen and then ining the separate hydrogen mixtures to a single ow just before passing into the Vycor tube. Several applied to the coated samples are summarized in the below.

FLAME SPRAY METHOD 7 EXAMPLE 3 LIIIB spray coatings upon titanium and titanium alloys :adily obtained in thicknesses of from 3 to 10 mils. his purpose, titanium samples as described in Ex- 1 are sprayed with silicon powder of less than 325 particles size, using a Wali-Colmonoy powder gun. found that well-bonded coatings of any desired 1ess in this range are obtainable in the hot spray of eated powder, the silicon being sintered by the heat e gun at a temperature in a range of about 1000 to C. If desired, the porosity and the bonding ;th of the coatings produced by this method may be what improved by further sintering, preferably in a rm furnace, or by further torch flaming. However, found that sufficiently good coatings are effected by dame spray procedure so that subsequent steps of ing, as in a vacuum furnace, are not essential. mparative results of flame spraying with coatings by methods above are listed in the table below.

CEMENTATlON METHOD EXAMPLE 4 nples of titanium base, prepared as described in tpie 1, are placed in a bed by packing the work piece ely powdered 325 mesh silicon disposed in a tube- Inconel furnace, the tube being rotated while heatt a rate of about 1 revolution per minute. The bed ated in the range of 900 to 1200 C. for a period of 30 hours to produce coatings ranging from 1 to 10 in thickness. During the heating period the silicon [er is mixed either with 2 /z% to 5% of iodine or sium iodide, or a mixture of both in equal proporthe mixture being preferred. Other volatilizable en compounds, such as alkali or alkaline earth metal es, or elementary halogen, may be used admixed the silicon of the bed or the halogen may be continiy supplied thereto as the heating proceeds. Prong in accordance with the present example, a samf titanium metal prepared as in Example 1 is emed in silicon powder containing 2 /&% each of eleal iodine and potassium iodide, and the bed is heated being rotated continuously and heat applied by y raising the temperature over a period of 6 hours 00 C., and maintaining that temperature for a furperiod of about 26 hours. A continuous coating of t 10 mils is obtained. Lesser periods of heating at what higher temperatures may be applied. This od is not as desirable as the others described herein- COMPARATIVE TESTS .e following table lists comparative results of sample ngs obtained in Examples 1 to 3.

Coating Test Hours of Coating Method of Temp Thick- Temp. 0t Heating Procedure Sintering C.) ness Heating Before (Mils) in Air Failure Uncoated 800 36 Example 1.-.. Vacuum 1 hr 1, 200 2. 0 800 l 240 Do d0 1,175 1.0 800 3 1,585 d0 1, 175 1. 0 800 1, 420 .do .275 2.0 800 3 1,560 Helium 1 hr..- 1,200 1.0 800 1, 275 Vacuum 1 hr 1, 350 2. 5 800 2, 160 Vapor Phase.' 1 995 1. 0 800 4 89 Do d0 1,325 1.0 1,000 787 Example 3 Flame Spray 10.0 1, 000 2,191

1 sintered only 5 minutes. sintered for 10 minutes. All samples were of titanium :Jt:l1lo1y50Itg130B except underlined Example 1, which was Hentin in alternate -second cycles with intermittent cooling. ther samples not so designated were heated continuously.

Sample still in test without failure.

As shown by the above, very desirable physical properties are imparted to titanium base metal by coating the same with an integral skin layer comprising an alloy or intermetallic composition of the silicon with titanium in which the silicide Ti Si is a predominant component. Of the many desirable properties of this coated product, the resistance to oxidation in air at high temperatures is outstanding. While the examples describe sheets in the several coating experiments, it will be apparent that various other shapes, such as bars, rods, tubes, plates, discs, pellets and the like, or irregular shapes, may be coated by the several procedures herein described.

Of the many procedures disclosed, certain give good coatings when the surface layer has a thickness in the lower range of A to 3 mils. Others, such as flame spraying, cementation, or hot dipping, give thicker coatings, such as from 2 to 15 mils, the thickness often being characteristic of the coating procedure, but any desired thickness may be effected, such as in the painting procedure, by repeating the coating process to obtain the same. A desirable guide for selection of proper thickness of coating and the procedure to obtain the same is the effectiveness and evenness with which the layer is bonded to impart satisfactory protection to the base metal at high temperatures without cracking, spalling, or blistering, etc. Certain of the coating procedures are outstanding because of the rapidity and economy of apparatus installations useful in effecting the coating. Others are preferred for their adaptability to coat large or irregular shapes without recourse to expensive apparatus. For relatively thin but highly effective coatings the painting method, as hereinabove stated, is preferred.

Many base metals, such as steel, nickel, molybdenum, etc., which are desirably modified to have some of the outstanding uses of titanium, may be first clad with titanium sheet or otherwise coated with titanium metal or alloy, and may thereafter have the titanium surface supplied with an exterior skin layer or coating of titanium silicides as herein described.

We claim:

1. The method of treating titanium metal bodies and alloys thereof to impart resistance thereto to the destructive action of gases at elevated temperatures comprising embedding the titanium metal base in finely powdered elemental silicon and heating the bed to a temperature in the range of about 900 to 1200 C. for a period sulficient to impart a coating thereto of at least 36 mil in thickness while supplying to said bed a catalyst compris ing a halogen substance selected from the group consisting of alkali and alkaline earth metal halides and elemental halogen.

2. The method as defined in claim 1 wherein the catalyst substance is mixed with the elemental silicon as a component of the bed in quantity ranging from about 2 /2% to 5% thereof.

3. The method of treating titanium metal bodies and alloys thereof to impart resistance thereto to the destructive action of gases at elevated temperatures, comprising painting the titanium body with a liquid coating composition comprising a carrier liquid having dissolved therein a heat-decomposable, temporary, organic binder substance and having suspended therein a mixture of finely powdered elemental silicon and finely powdered elemental titanium, drying the coated body and heating the same in an inert atmosphere to decompose and volatilize the binder substance and sinter the silicon to convert the same to an integral exterior layer on the titanium comprising an alloy or intermetallic composition of silicon and titanium.

4. The method of treating titanium metal bodies and alloys thereof to impart resistance thereto to the destructive action of gases at elevated temperatures, comprising painting the titanium body with a liquid coating composition comprising a carrier liquid having dissolved therein a heat-decomposable, temporary, organic binder substance and having suspended therein a pre-sintered mixture of titanium and silicon containing substantial quantities of Ti Si drying the coated body and heating the same in an inert atmosphere to decompose and volatilize the binder substance and sinter the silicon to convert the same to an integral exterior layer on the titanium prising an alloy or intermetallic composition of and titanium.

5 References Cited in the file of this patent UNITED STATES PATENTS 2,109,485 lhrig Mar. 1, 2,289,614 Wesley et al July 14, 10 2,501,051 Henderson Mar. 21, 2,541,813 Frisch et al Feb. 13, 2,554,042 Mayfield May 22, 2,665,997 Campbell et al Jan. 12 2,674,542 Alexander Apr. 6, 15 2,755,199 Rossheim et al. July 17,

OTHER REFERENCES Burns et al.: Protective Coatings for Metals, Rel Pub. Co. (1939), Page 42.

Campbell et al.: The Vapor Phase Deposition fractory Metals, Transactions of The Electrocht Society, vol. 96, November 1949, pp. 318-333.

Mesick: Journal of Metals, vol. 5, February 195 Steel, vol. 133, #18, Nov. 2, 1953, pp. -132. 

3. THE METHOD OF TREATING TITANIUM METAL BODIES AND ALLOYS THEREOF TO IMPART RESISTANCE THERETO TO THE DESTRUCTIVE ACTION OF GASES AT ELEVATED TEMPERATURES, COMPRISING PAINTING THE TITANIUM BODY WITH A LIQUID COATING COMPOSITION COMPRISING A CARRIER LIQUID HAVING DISSOLVED THEREIN A HEAT-DECOMPOSABLE, TEMPORARY, ORGANIC BINDER SUBSTANCE AND HAVING SUSPENDED THEREIN A MIXTURE OF FINELY POWDERED ELEMENTAL SILICON AND FINELY POWDERED ELEMENTAL TITANIUM, DRYING THE COATED BODY AND HEATING THE SAME IN AN INERT ATMOSPHERE TO DECOMPOSE AND VOLATILIZE THE BINDER SUBSTANCE AND SINTER THE SILICON TO CONVERT THE SAME TO AN INTEGRAL EXTERIOR LAYER ON THE TITANIUM COMPRISING AN ALLOY OR INTERMETALLIC COMPOSITION OF SILICON AND TITANIUM. 